1. Field of the Invention
The present invention relates to a coaxial connector and a communication device, and more particularly to a coaxial connector for use in, for example, mobile communication devices such as portable telephones, etc., and to be able to change signal lines, and a communication device including such a coaxial connector.
2. Description of the Related Art
Up to now, in communication devices such as portable telephones, etc., there are cases in which a surface-mount type coaxial connector having a function for changing signal lines is used. The present applicant has proposed various coaxial connectors having such a switching function disclosed in Japanese Unexamined Patent Application Publication No. 9-245907, Japanese Patent No. 3064906, Japanese Unexamined Patent Application Publication No. 11-265761, Japanese Unexamined Patent Application Publication No. 2002-359032, and others.
As shown in FIG. 9, such a coaxial connector is basically constructed such that a movable terminal 92 made of a conductive thin plate, a fixed terminal 93, and an external terminal 94 are attached to an insulating case 91, and a contact portion 92a at the tip of the movable terminal 92 is arranged so as to be generally in contact with the contact portion 93a of the fixed terminal 93 by the elastic restoring force of the thin plate.
When a probe 80 for measuring characteristics is mounted, the central contact 81 is put in through the opening portion 95 of the insulating case 91, the movable terminal 92 is displaced downward by the central contact 81 (see the dotted line in FIG. 9), the contact portion 92a is disconnected from the contact portion 93a, and then the signal line is changed from the fixed terminal 93 to the central contact 81. At the same time, the external conductor 82 comes into contact with the external terminal 94, which is grounded.
On the other hand, a coaxial connector in which a magnetic force is utilized to perform a switching operation (changing signal lines) is described in Japanese Unexamined Patent Application Publication No. 2002-359032.
In a related coaxial connector 90 shown in FIG. 9, the opening and closing of the contact portions 92a and 93a are performed by the spring function of the movable terminal 92. Then, with a coaxial connector 90, which has a small size and a reduced height, it is difficult to obtain a sufficient stroke of the movable contact portion 92a. On the contrary, if a sufficient stroke is secured, the total length of the movable portion of a spring becomes larger and the contact pressure becomes smaller.
Accordingly, it is necessary to reduce the total length of the movable portion of a spring to a certain extent in order to secure a necessary contact pressure. However, in a short movable spring portion, plastic deformation may occur and the contacting reliability cannot be ensured. In order to prevent the plastic deformation, it may be considered to limit the stroke, but further shortening the originally small stroke makes the gap between the contact portions shorter, which may cause unstable disconnection.
On the other hand, in a coaxial connector using the magnetic force described in Japanese Unexamined Patent Application Publication No. 2002-359032, since a part of the magnetic circuit is made open, the efficiency of making use of the magnetic flux is not necessarily high.
In order to overcome the problems described above, preferred embodiments of the present invention provide a low-cost, compact coaxial connector, in which the efficiency of making use of the magnetic flux is high and the reliability of contacting of the movable terminal to the fixed terminal is excellent, and also provide a communication device including such a novel connector. Also, preferred embodiments of the present invention provide a low-cost, compact coaxial connector as described in the preceding sentence that also has a reduced number of parts, requires much fewer man-hours for production, and which can be produced at a greatly reduced cost, and also provide a communication device including such a novel connector. In addition, preferred embodiments of the present invention provide a low-cost compact coaxial connector as described in the preceding sentences, and which can prevent corrosion of the contact portions, increase and secure the reliability of contact, and have terminal portions thereof be reliably soldered, and also provide a communication device including such a connector.
According to a preferred embodiment of the present invention, a coaxial connector includes switching signal lines with a probe having a central contact and an external conductor, the probe being mounted thereto or dismounted therefrom, and including a first fixed yoke terminal made of a conductive magnetic material, a second fixed yoke terminal made of a conductive magnetic material, a movable terminal made of a conductive magnetic material, and a permanent magnet made of a ferromagnetic material. In the coaxial connector, the first fixed yoke terminal, the second fixed yoke terminal, the movable terminal, and the permanent magnet constitute a magnetic circuit, at least one mechanical contact portion is provided between the first and second fixed yoke terminals in the magnetic circuit, and the contact portion is connected by the magnetic force of the permanent magnet when the probe is dismounted and the contact portion is disconnected by the movable terminal being pressed by the central contact when the probe is mounted.
In the coaxial connector of a preferred embodiment of the present invention, a signal line is provided in the magnetic circuit defined by the first fixed yoke terminal, the second fixed yoke terminal, the movable terminal, and the permanent magnet so as to have at least one mechanical contact portion. This contact portion is changed to a connected state by the magnetic force of the permanent magnet to form a closed magnetic circuit, and, since the efficiency of using the magnetic flux is high, a stable connected state can be maintained. Then, since the contact portion is disconnected by the central contact pressing the movable terminal when the probe is mounted, the performance of the disconnection is reliable.
In a coaxial connector of a preferred embodiment of the present invention, when the contact portion is connected, the first fixed yoke terminal and the second fixed yoke terminal are electrically connected through the movable terminal and, when the contact portion is disconnected, the first fixed yoke terminal and the second fixed yoke terminal are electrically disconnected. The construction of the coaxial connector, in which the magnetic circuit and the signal line are combined into one, becomes compact, the number of parts and the number of man-hours required for manufacturing are also reduced, and it becomes possible to build the coaxial connector at low cost.
Furthermore, the contact portion being disconnected returns to the contact portion being connected by the magnetic force of the permanent magnet. Since the maintenance of the contact pressure and the return to the connected state from the disconnected state are performed by the magnetic force, even if the opening and closing of the contact portion are repeated, the contact pressure hardly changes and the opening and closing operation can be stably performed.
The permanent magnet has anisotropic magnetic characteristics. In the anisotropic permanent magnet, the flux centers on the magnetic pole surfaces and leakage of the magnetic flux is reduced. As a result, the contact pressure increases.
The first fixed yoke terminal and the second fixed yoke terminal are integrally provided with input-output terminals for an electrical signal. The number of parts and the number of man-hours required for production are reduced.
Furthermore, the direction of the magnetic flux passing through the movable terminal is substantially perpendicular to the magnetization direction of the permanent magnet. The movable terminal is disposed between the N pole and S pole of the permanent magnet and the movable contact portion is also positioned in the vicinity of the neutral point of the magnet. Accordingly, the movable terminal is prevented from being attracted by the magnet because of leakage of the magnetic flux and the movable contact portion reliably returns to a contacting state.
The magnetic flux passing through between the movable terminal and the first fixed yoke terminal or the second fixed yoke terminal may be larger than the magnetic flux passing through between the movable terminal and the permanent magnet. The movable contact portion reliably returns to a contacting state.
Moreover, the first fixed yoke terminal, the second fixed yoke terminal, and the movable terminal are nickel-plated as a foundation coat and are gold-plated as a top coat. A cold rolling steel plate is preferably used for cost-efficiency in these terminals, but corrosion of the terminals is prevented by nickel plating and gold plating, and the solderability and contact reliability increase.
Furthermore, a communication device according to another preferred embodiment of the present invention includes a coaxial connector according to the preferred embodiments of the present invention described above. Thus, the communication device has the advantages of the improved contact reliability of the coaxial connector and the other advantages described above.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.